I've just got one of these things; it's not actually a Trail Gator but
a similar German device called Profex. Unfortunately the instructions
are in German, which I don't read
The bar is attached to the seat post of the adult bike. I'm not sure
whether it's supposed to pivot around the bar. It's almost impossible
to stop it doing so, but the effect is that the child's bike then
moves off centre, and tries to pull the adult bike off to one side. I
was wondering whether perhaps the joint should be quite loose, so that
if the child's bike does wander off centre, it will quickly wander
back again.
I have actually managed to get it so it doesn't move, by strapping it
to the bike rack. This feels OK, but you can't turn in a tight circle.